The power transmitting apparatus of a vehicle, such as an automobile, is required not only to perform transmission of engine power of the automobile to the wheels but also to permit radial, axial and moment displacement from the wheels caused during bounds in rough road running or turning of the vehicle. Accordingly, one end of a drive shaft, interposed between an engine side and a driving wheel side, is connected to a differential gear via a constant velocity universal joint of the sliding type. The other end is connected to driving wheels via a wheel bearing apparatus including a fixed type constant velocity universal joint. In addition, components not required to transmit the power to the wheels are connected to driven wheels via the wheel bearing apparatus.
The wheel bearing apparatus is usually fit into a knuckle forming part of the suspension apparatus. The knuckle is formed with mounting portions, to secure the wheel bearing apparatus, and openings, for passing rotational members such as the drive shaft and constant velocity universal joint. Rain water, etc. enters into the fitting surfaces between the knuckle and the wheel bearing apparatus through annular spaces formed between the rotational members and the knuckle. In addition, rain water etc. enters into the inside of the wheel bearing apparatus through its securing portions in the knuckle which forms a closing lid for the wheel bearing apparatus.
Seals are mounted between the outer and inner members of the wheel bearing apparatus to prevent rain water etc. from entering into the wheel bearing apparatus. However, it is impossible to prevent the entry of rain water etc. through the fitting portion between the knuckle and the outer member fit into the knuckle. Accordingly, rust is sometimes generated in the fitting portion between the knuckle and the outer member. Thus, removal of the wheel bearing apparatus from the knuckle becomes difficult. In addition to this problem, it is necessary to add a new seal in the knuckle of the closing lid type knuckle and thus the number of parts is increased.
Furthermore, when using a knuckle of an aluminum alloy to reduce its weight, electric corrosion is generated by rain water etc. that enters into the fitting portion between the steel knuckle and the aluminum alloy outer member. Thus, it is necessary to surely prevent entry of rain water etc. into the fitting portion between the knuckle and the outer member.
A device for solving such a problem is shown in FIG. 10. The wheel bearing apparatus includes a wheel hub 51 and a wheel bearing 52 fit into the wheel hub 51. The wheel bearing 52 has an outer member 54 fit into an aluminum alloy knuckle 53. A pair of inner rings 56 is inserted into the outer member 54 via double row balls 55, 55. The wheel hub 51 has, on its one end, a wheel mounting flange 57 with hub bolts 57a mounted equidistantly along its outer circumference. A wheel W is mounted thereto via a brake rotor R.
A constant velocity universal joint 58 includes an outer joint member 59, a joint inner ring (not shown), a cage, and torque transmitting balls. The outer joint member 59 is formed with an integrated body including a cup-shaped mouth portion 60, a shoulder portion 61, forming a bottom of the mouth portion 60, and a stem portion 62 axially extending from the shoulder portion 61. The stem portion 62 is formed with a serration 62a on its outer circumference. An external thread 62b is at the end of the serration 62a. The wheel hub 51 and the outer joint member 59 are detachably united by a securing nut 63. The end face of the inner ring 56 abuts against the shoulder portion 61 of the outer joint member 59.
Seals 64, 65 are mounted in an annular space opening formed between the outer member 54 and the inner ring 56. The seals 64, 65 prevent leakage of grease sealed in the wheel bearing and the entry of rain water, dust etc. into the inside of the wheel bearing from the outside.
As shown in a partially enlarged view of FIG. 11, a knuckle opening 66 has a larger inner circumference 66a, a smaller inner circumference 66b, and a stepped surface 66c. The small inner circumference 66b has an inner diameter slightly smaller than that of the larger inner circumference 66a. The stepped surface 66c is positioned between the larger and smaller inner circumferences 66a, 66b. The seal 65 includes a metal core 67, a first seal portion 68, a second seal portion 69, a cover portion 70, and a slinger 71.
The metal core 67 is adapted to be press-fit into the inner circumference of the end of the outer member 54. The metal core 67 radially inner end extends toward the outer circumference of the inner ring 56. The first seal portion 68 is formed of non-conductive material such as synthetic rubber etc. and has three sealing lips that extend in three directions so as to be in sliding contact with the slinger 71. The slinger 72 is press-fit onto the outer circumference of the inner ring 56. The second seal portion 69 is formed of non-conductive material such as synthetic rubber etc. The second seal portion 69 has a packing-like sealing lip adapted to be press-contacted to the stepped surface 66c in the opening 66 of the knuckle 53. The cover portion 70 is formed of non-conductive material such as synthetic rubber and covers the metal core 67 between the first seal portion 68 and the second seal portion 69.
Rain water etc. splashed between a space between the knuckle 53 and the constant velocity universal joint 58, during running of a vehicle, would enter through the opening 66 of the knuckle 53 into an opening between the outer member 54 and the inner ring 56 and into a gap in the fitting portion 72 between the outer member 54 and the knuckle 53.
Under these circumstances, the entry of rain water etc. into the inside of the wheel bearing can be prevented by closure of the opening between the outer member 54 and the inner ring 56 due to cooperation of the first seal portion 68 and the slinger 71.
In addition, the entry of rain water etc. into the gap in the fitting portion 72 between the outer member 54 and the knuckle 53 can also be prevented by closure of the space between the outer member 54 and the knuckle 53 due to cooperation of the second seal portion 69 and the stepped surface 66c of the knuckle 53. Thus, the generation of electric corrosion in the fitting portion 72 between the knuckle 53 and the outer member 54 can be surely prevented without adding seals and increasing the number of components. See, Japanese Laid-open Patent Publication No. 172912/2002.
In such a prior art wheel bearing apparatus, the packing-like sealing lip of the second seal portion 69 is formed with a projected outline to be press-contacted with the stepped surface 66c of the knuckle 53. Thus, it tends to be in contact with other components. Specifically, it is damaged during assembling steps and transportation of the wheel bearing or assembling of the wheel bearing apparatus to a vehicle. This causes problems not only with difficulties in handling, deterioration of assembling efficiency but also of a reduction of reliability in quality.